The present invention relates to a probe and anchoring device for anchoring the probe in a well.
Probes having deployable arms, known in the prior art, generally have one or two arms which are located on the same generatrix of the probe body.
When such probes are equipped with two unidirectional measuring elements sensitive to the movements of the well walls, these measuring elements are placed such that the plane defined by deployment of the arms is a plane bisecting the measuring axes of each of these elements. The deployment plane contains the probe axis. The measuring axes are generally perpendicular to each other and intersect the axis of the probe at the same point.
Thus, according to the prior art, the probe and its arms touch the wall along a plane. Although this arrangement does transmit to the measuring elements the movements of the geological formation which are contained in this plane, it only poorly transmits the movements not contained therein, particularly those perpendicular to this plane.
In the latter case, the stiffness of the probe plus anchoring arm assembly is low and parasitic movements, particularly vibrations due to this lack of stiffness, are detected by the measuring elements.
Thus, the present invention relates to a device for anchoring a probe in a well, with the probe having an axis parallel to the well axis and having a probe body which supports anchoring device provided with arms.
In addition, this anchoring device has, essentially at the same level as the probe axis, two arms offset angularly with respect to each other relative to the axis of the probe. The arms are disposed such that, when they are deployed, the probe comes directly into contact with the well walls.
A portion of the outer wall of the probe body, essentially adjacent to the plane bisecting the deployment planes of the arms, and opposite the latter, can be designed to permit good direct attachment of said body to the well walls.
Preferably, the arms can be offset by an angle of 90.degree. with respect to the axis of said probe or may be offset by an angle of 120.degree..
The device according to the invention may have two other arms located at a different level than that of the first two arms.
The two levels may be located on either side of the measuring element with which the probe is equipped.
The present invention also relates to a probe equipped with the anchoring device described above, with the probe may have at least one directional measuring element operating in the plane defined by deployment of one of the arms.
The deployment plane of one of the arms may contain the probe axis.
The measuring direction of one of the measuring elements may be substantially perpendicular to the axis of the probe.
At least one measuring element of the probe may be located substantially in the vicinity of one of the levels.
The probe according to the present invention may comprise two unidirectional measuring elements, one of which may operate in a plane defined by the deployment of one of the arms and the other may operate in the plane of deployment of another arm.
The probe according to the invention may comprise a third unidirectional measuring element.
The arms may be placed at the same level as the probe axis and at least one measuring element may be placed substantially in the vicinity of this same level and effect measurements in directions substantially perpendicular to the probe axis.
Preferably two and possibly three elements may make measurements in a direction perpendicular to the probe axis.
The probe according to the present invention may also have a unidirectional measuring element oriented along the probe axis.
The present invention may advantageously be applied to the oil sector. Thus, it may be applied to drilling wells made either for prospecting or for production. The measurements made may be seismic measurements or pickups of fracturing, etc. The measuring elements may in particular be geophones or accelerometers.
According to one important characteristic of the present invention, the probe body is in direct contact with the walls of the well and generally substantially along one generatrix thereof.